Printed circuit board, method of manufacturing same, and method of mounting the circuit board in a connector socket

ABSTRACT

A circuit board that is to be mounted in a connector socket includes a plurality of electrical connectors located along a side edge of the circuit board. Retention bosses are formed on first and second opposite sides of the circuit board, each of the retention bosses protruding from a surface of the circuit board and extending parallel to and adjacent to the first edge of the circuit board. When the first edge of the circuit board is inserted into a slot of a connector socket, contact surfaces of the first and second retention bosses contact top surfaces of the connector socket to help immobilize the circuit board with respect to the connector socket. Adhesive layers on the contact surfaces of the first and second retention bosses may adhere to the top surfaces of the connector socket to help hold the circuit board immobile with respect to the connector socket.

This application is a continuation of U.S. application Ser. No.13/933,288, filed Jul. 2, 2013, the entire contents of which is herebyincorporated by reference.

BACKGROUND

This application relates to methods of manufacturing and mounting aprinted circuit board in a receiving socket such that electrical leadson the printed circuit board maintain good electrical connections withpins in the receiving socket. In particular, the application isconcerned with creating a mounting structure that will ensure goodelectrical connections are maintained even when the assembly issubjected to significant levels of shock and vibration.

A printed circuit board (PCB) both mechanically supports andelectrically connects electronic components. A PCB may include one ormore non-conductive layers which provide mechanical support andelectrical separation/insulation for one or more conductive layers. Theone or more conductive layers, for example, may include any electricallyconductive material such as copper, silver, aluminum, etc. Theconductive layers may be formed on the PCB in patterns that allow leadsof selected electrical components that are mounted on the PCB to beelectrically connected to one another.

FIGS. 1A and 1B illustrate a related art PCB 1, and a mounting socket 2that receives the PCB. The PCB 1 includes a substrate 11, electroniccomponents 12, and a plurality of electrical leads 13 formed along thelower edge of the substrate 11. Electrical components 12 can be formedon both sides of the substrate. Likewise, separate electrical leads 13may be formed on opposite sides of the substrate. Conductive layers ortraces on the substrate electrically connect leads of the electricalcomponents 12 to the electrical leads 13 on the bottom edge of thesubstrate.

The PCB is mounted in the socket 2 by pushing the lower edge of the PCBinto a slot 22 formed between sidewalls 25 of the socket 2, asillustrated in FIG. 1B. Electrical contacts or pins in the slot 22couple to the electrical leads 13 on sides of the bottom edge of the PCB1. The socket may also include pivoting locking clips 21 that engageslots 15 on side edges of the PCB to hold the PCB 1 in the socket 2.When the locking clips 21 are pivoted outward away from the side edgesof the PCB 1, they may exert an upward force on the bottom edge of thePCB 1 that tends to push the PCB 1 out of the slot 22 of the socket 2.

Unfortunately, when a PCB 1 and mounting slot 2 arrangement as shown inFIGS. 1A and 1B are subjected to significant levels of shock andvibration, the PCB 1 can move with respect to the mounting socket 2.This movement of the PCB 1 can cause an electrical connection betweenthe electrical leads 13 on the bottom edge of the PCB 1 and contacts inthe slot 22 to be broken temporarily broken or impaired. Althoughcontact between the electrical contacts 13 and the leads in the slot 22may not be completely broken, movements of the PCB 1 with respect to themounting slot 22 may cause the electrical resistance of the connectionto vary over time. And this change in electrical resistance alone couldcause problems for signals traversing the connection. As a result ofthese factors, when such an assembly is subjected to significant shockand vibration, it is common for an electrical computing system usingthis arrangement to report faults or errors, or completely stopresponding.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B illustrated a background art PCB and mounting socket;

FIGS. 2A and 2B are perspective views of opposite sides of a firstembodiment of a PCB having retention bosses that is positioned above amounting slot;

FIG. 3 is a side view of PCB having retention bosses mounted in amounting slot;

FIG. 4 is a cross-sectional view of a PCB having retention bassesmounted in a mounting slot;

FIG. 5 is a perspective view of a PCB with discontinuous sections of aretention boss;

FIG. 6A-6C are cross-sectional views illustrating alternatecross-sectional shapes of retention bosses; and

FIG. 7 illustrates steps of a method of forming a PCB with retentionbosses.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

A detailed description of exemplary embodiments is provided withreference to the accompanying drawings. Like reference numerals indicatelike parts throughout the drawings.

FIGS. 2A and 2B illustrate a printed circuit board (PCB) 100 positionedabove a mounting socket. FIG. 2A shows a first side 110 of the PCB 100,and FIG. 2B shows a second, opposite side 120 of the PCB 100. Asdescribed above, a variety of electrical components would be mounted onone or both of the first and second sides 110, 120 of the PCB 100.Electrically conductive layers or traces would couple those electricalcomponents to electrical leads 130 formed on the bottom edge of the PCB100. For ease of illustration, however, the electrical components andelectrically conductive leads and traces are not shown.

One or more retention bosses are formed on the sides of the PCB 100. Inthe embodiment illustrated in FIGS. 2A and 2B, a first retention boss 30is formed on the first side 110 of the PCB 100, and a second retentionboss 40 is formed on the second side 120 of the PCB. The first andsecond retention bosses 30, 40 are formed adjacent the lower edge of thePCB, above the electrical leads 130. FIG. 3 shows the PCB 100 after ithas been inserted into the mounting slot 22 of a mounting socket 2. Oncethe PCB 100 is inserted into the mounting slot 22, lower surfaces 35, 45of the first and second retention bosses 30, 40 abut upper surfaces 25of the mounting socket 2 on opposite sides of the mounting slot 22.

The presence of the first and second retention bosses 30, 40 helps tostabilize the PCB 100 with respect to the mounting socket 2 when theassembly is subjected to shock and vibration. Because bottom surfaces35, 45 of the first and second retention bosses 30, 40 abut the uppersurfaces 25 of the mounting socket 2, the PCB is less likely to wobblein the slot 22, or to rotate around the lower edge of the PCB, when theassembly is subjected to shock and vibration. Any rotation of the PCBthat does occur is likely to be a pivoting movement around the uppersurfaces 25 of the mounting socket 2, instead of a point lower downwhere the electrical leads 130 on the PCB are located. As a result, thebottom edge of the PCB and the electrical leads tend to move laterallyfrom side to side against the bias of the electrical contacts 27 in thereceiving slot 22 of the mounting socket 2. These aspects of the designcause any movements of the bottom edge of the PCB to smaller thanmovements that would occur if the retention bosses 30, 40 were notpresent. As a result, the electrical connections between the electricalleads 130 on the PCB and the electrical contacts 27 in the mountingsocket 2 are better maintained when the assembly is subjected to shockand vibration.

The retention bosses 30, 40 may be any length. In some embodiments, theretention bosses may run along substantially the entire length of thePCB. In alternate embodiments, the retention bosses may only extendalong a portion of the length of the PCB. In still other embodiments,two or more discontinuous segments of a retention boss may be formedalong a single side of the PCB.

For example, FIG. 5 illustrates a PCB 100 with three discontinuoussegments 50, 52, 54 of a retention boss formed on one side of the PCB.The retention boss may be made discontinuous to avoid covering up anelectrical component that requires air cooling for proper operation.Alternatively, it may be advantageous to form only a few segments of theretention boss along the length of the PCB to minimize the weight of theassembly, or to reduce material consumption. Several separate segmentsof a retention boss formed along the length of the retention boss mayprovide most of the immobilizing benefits as a continuous retention bossformed along the entire length of the PCB.

In some embodiments, the length of the first retention boss 30 iscontrolled such that first and second end surfaces 34, 36 of the firstretention boss 30 engage corresponding inner surfaces 24, 26 of themounting socket. Likewise, a length of the second retention boss 40 iscontrolled such that first and second end surfaces 44, 46 of the secondretention boss 40 engage corresponding inner surfaces 24, 26 of themounting socket. The engagement between the first and second endsurfaces of the retention bosses and the corresponding inner surfaces ofthe mounting socket 2 may also help to keep the PCB 100 from moving withrespect to the mounting socket 2.

In some embodiments, an adhesive layer may be formed along the bottomsurfaces 35, 45 of the first and second retention bosses 30, 40. When aPCB 100 having this configuration is mounted in a mounting slot 22 of amounting socket 2, the adhesive layer bonds to the upper surfaces 25 ofthe mounting socket 2 on opposite sides of the mounting slot 22, whichhelps to further immobilize the PCB with respect to the mounting socket.FIG. 4 shows a cross-sectional view of a PCB 100 having thisconfiguration.

As shown in FIG. 4, an adhesive layer 37 is formed on the lower surfaceof the first retention boss, and an adhesive layer 47 is formed on abottom surface of the second retention boss 40. The adhesive layers 37,47 bond to the top surfaces 25 of the mounting socket 2 located onopposite sides of the mounting slot 22. FIG. 4 also illustrates howelectrical contacts 27 in the mounting slot 22 contact electrical leadson the bottom edge of the PCB 100.

Adhesive layers may also be provided on the end surfaces 34, 36, 44, 46of the retention bosses. Such adhesive layers would bond to thecorresponding inner side surfaces 24, 26 of the mounting socket 2 tohelp keep the PCB immobilized with respect to the mounting socket.

When adhesive layers are provided on surfaces of the retention bosses,the adhesive layers may initially be covered by a removable protectivefilm. When one wishes to mount the PCB in a mounting socket, one wouldremove the protective film, then insert the PCB 100 into the mountingslot of the mounting socket until the adhesive layers contact and adhereto corresponding surfaces of the mounting socket.

The width of the bottom surfaces 35, 45 of the retention bosses 40, 50,may be greater than, equal to, or less than a width of the uppersurfaces 25 of the mounting socket located on opposite sides of the slot22 of the mounting socket 2.

As illustrated in FIG. 4, a cross-sectional shape of the retentionbosses 30, 40 may be square or rectangular. However, the retentionbosses could also have many other cross-sectional shapes.

For example, FIG. 6A shows a PCB 100 with retention bosses 60, 62 havinga triangular cross-sectional shape. FIG. 6B illustrates a PCB 100 withretention bosses 64, 66 having convex side surfaces. FIG. 6C illustratesa OCB 100 having retention bosses with concave side surfaces. Of course,many other cross-sectional shapes are also possible.

The retention bosses can be formed of any suitable material which doesnot interfere with the proper operation of the PCB 100. In someembodiments, it may be desirable for the material of the retentionbosses to be electrically insulative, such that the retention bosses donot interfere with or short circuit any of the electrical components,conductive layers or traces that are formed on the PCB.

In some embodiments, the retention bosses may be formed of a moldingresin, such as an epoxy resin. The resin preferably has a relativelyhigh electrical resistivity, which helps to prevent any short circuitingof any electrical components, leads or metal traces covered by theresin.

In some embodiments, the retention bosses may be formed of a materialthat is semi-rigid. In these embodiments, it may be desirable to formthe retention bosses such that they have a length that is slightlylonger than the distance between the interior side surfaces 24, 26 ofthe mounting socket. As a result, the retention bosses will be slightlycompressed and deformed when the PCB is inserted into the mountingsocket. This will provide an interference fit that helps to keep the PCBimmobilized with respect to the mounting socket.

In the embodiments described thus far, retention bosses are formed onopposite sides 110, 120 of a PCB 100. However, in alternate embodiments,a retention boss may be formed on only one side of a PCB. Further, ifretention bosses are formed on opposite sides of a PCB, the retentionboss on a first side of the PCB may have a different configuration thana retention boss on the opposite side of the PCB.

FIG. 7 illustrates steps of forming a PCB having retention bosses. Themethod begins in step S702, when a PCB is inserted into a mold havingone or more cavities that are configured to form the retention bosses.In step S704, a molding resin is inserted into the mold cavities. Instep S706, the resin is allowed to cure. The PCB with the cured resinretention bosses is then removed from the mold.

In an optional final step S708, an adhesive is applied to selectedsurfaces of the retention bosses. As noted above, the surfaces of theadhesive opposite the retention bosses may be covered with a removableprotective film.

The forgoing exemplary embodiments are intended to provide anunderstanding of the disclosure to one of ordinary skill in the art. Theforgoing description is not intended to limit the inventive conceptdescribed in this application, the scope of which is defined in thefollowing claims.

What is claimed is:
 1. A printed circuit board, comprising: a substrateconfigured to support a plurality of electronic components; electricalcontacts located along a first edge of the substrate; a retention bossthat is located on a first surface of the substrate, the retention bossprotruding from the first surface and having a narrow, elongated shapethat extends parallel to and adjacent the first edge such that amajority of the first surface of the substrate is not covered by theretention boss, the retention boss including a contact surface that isconfigured to contact a surface of a connector socket when the firstedge of the substrate is inserted into the connector socket; and a firstadhesive layer on the contact surface of the retention boss.
 2. Thecircuit board of claim 1, further comprising a removable cover layermounted on the first adhesive layer.
 3. The circuit board of claim 1,wherein the retention boss comprises a first retention boss, and furthercomprising a second retention boss located on a second surface of thesubstrate that is opposite the first surface, the second retention bossprotruding from the second surface and having a narrow, elongated shapethat extends parallel to and adjacent the first edge such that amajority of the second surface of the substrate is not covered by thesecond retention boss, the second retention boss including a contactsurface that is configured to contact a surface of a connector socketwhen the first edge of the substrate is inserted into the connectorsocket.
 4. The circuit board of claim 3, further comprising a secondadhesive layer on the contact surface of the second retention boss. 5.The circuit board of claim 4, further comprising first and secondremovable cover layers mounted on the first and second adhesive layers,respectively.
 6. The printed circuit board of claim 1, wherein theretention boss comprises a moldable resin.
 7. The printed circuit boardof claim 6, wherein the moldable resin is electrically insulating. 8.The printed circuit board of claim 1, wherein the substrate comprises aninline memory module having a plurality of semiconductor memory modulesmounted thereon.
 9. A method of forming at least one retention boss onat least one surface of a circuit board having electrical contactslocated along a first edge of the circuit board, the method comprising:inserting the circuit board into a mold having a cavity that isconfigured to form a retention boss on a first surface of the circuitboard such that the retention boss protrudes from the first surface andhas a narrow, elongated shape that extends parallel to and adjacent thefirst edge such that a majority of the first surface of the substrate isnot covered by the retention boss; filling the mold cavity with amoldable material; allowing the moldable material to cure and therebyform a retention boss on the first surface, the retention boss includinga contact surface that is configured to contact a surface of a connectorsocket when the first edge of the circuit board is inserted into theconnector socket; removing the circuit board from the mold; and applyinga first adhesive layer to the contact surface of the retention boss. 10.The method of claim 9, wherein the filling step comprises filling themold cavity with a moldable resin material that hardens when it cures.11. The method of claim 9, wherein the inserting step comprisesinserting the circuit board into a mold having first and second cavitiesthat are configured to form first and second retention bosses,respectively, on first and second opposite surfaces of the circuit boardsuch that the first and second retention bosses protrude from the firstand second surfaces and have narrow, elongated shapes that extendparallel to and adjacent the first edge such that the majority of thefirst and second surfaces are not covered by the first and secondretention bosses, respectively, wherein the filling step comprisesfilling the first and second mold cavities with a moldable material, andwherein the allowing step comprises allowing the moldable material tocure and thereby form first and second retention bosses on the first andsecond surfaces of the circuit board, respectively, the first and secondretention bosses each including a contact surface that is configured tocontact a surface of a connector socket when the first edge of thecircuit board is inserted into the connector socket.
 12. The method ofclaim 11, wherein the applying step comprises applying first and secondadhesive layers to the contact surfaces of the first and secondretention bosses, respectively.